The present invention relates to an oven for dental prostheses or partial dental prostheses comprising a firing chamber and a heating device arranged in the firing chamber and having a heating filament formed from a suitable heating wire and a carrier for the heating filament.
With known ovens of the named kind, a tubular glass filament guided around at the inner side of the firing chamber is used and a likewise coiled heating wire is arranged in it. The heating filament has good guidance and protection in this manner. The heating device can also be replaced simply and no direct energy transfer to the walls of the firing chamber takes place.
It is disadvantageous with a heating device of this type, however, that the carrier filament has to be manufactured of quartz glass since the ovens are also operated with underpressure in the firing chamber so that essentially only the radiant heat is available. However, some of the radiation is also absorbed on the use of quartz glass. The quartz glass can additionally fog up or even become dull.
In other ovens for dental prostheses or partial dental prostheses, the heating filament is embedded in the walls of the firing chamber. Since the coefficient of expansion of the heating filament and of the wall material differ from one another, there is the risk that the wall material will crack. Furthermore, the embedded heating filament also emits energy directly to the walls in a substantial degree so that strong heat losses arise. A further disadvantage consists of the fact that the radiation of the embedded parts of the heating filament cannot be used. Finally, the exchange of the heating device is also difficult since the heating filament can only be replaced, if at all, together with the embedding mass.